cBN is known to have a hardness second to diamond and other characteristics such as high thermal conductivity and low affinity to ferrous materials, and sintered bodies composed of cBN are being used in cutting tools.
cBN sintered bodies used in cutting tools can be roughly categorized into two types based on composition, namely, high-cBN-content sintered bodies and low-cBN-content sintered bodies. The former has a high cBN particle content and has a sintered body structure in which cBN particles directly bond to each other and the rest is bonded with a binder containing Co or Al as a main component. In contrast, the latter has a low cBN particle content and has a sintered body structure in which there are fewer portions where cBN particles come into contact with one another and thus particles bond to each other via a ceramic material such as TiN or TiC.
An example of the high-cBN-content sintered bodies is a cBN sintered body disclosed in PTL 1 including 88% to 97% by volume of cBN, a bonding phase, and unavoidable impurities.